Vehicle conveyors used in car washes are well known and form an important part of a car wash system. Car wash conveyors must be rugged and dependable. They also must be suitable for use in the harsh car wash environment wherein water, detergent and dirt are constantly in contact with the conveyor and its component parts.
One example of a car wash conveyor is disclosed in U.S. Pat. No. 4,576,098 to Belanger et al., issued Mar. 18, 1986, which is owned by the assignee of the present application. The conveyor includes a framework in which there is provided an endless sprocket chain conveyor assembly having thereon a series of longitudinally spaced roller dollies (also called roller mechanisms or pushers) which for normal operation are movably positioned within the framework below a top platform or track over which a vehicle tire is adapted to advance. An automotive vehicle sensing device and a programmable power operated ramp or elevator are provided whereby a vehicle will activate the sensing device which is effective to raise the ramp or elevator. This results in an advancing roller dolly or pusher being deflected by the ramp onto the top platform or track where the roller dolly engages the vehicle tire and movably advances the vehicle along the track. The roller dollies do not have a low profile and do not move upwardly or downwardly relative to the top platform when the roller dolly engages the tire of the vehicle to be transported. The roller dollies do not conform to the shape of the sprocket as they move about the sprocket.
Another example of a vehicle conveyor is shown in the Hanna's U.S. Pat. No. 3,554,132, issued Jan. 12, 1971 and reissued as U.S. Pat. No. Re. 30,026 on June 12, 1979. This patent discloses an endless conveyor chain carrying roller dollies or pushers which is mounted for travel below a vehicle path. The pushers are below and are movable by a selectively operable guide to the level of the path when the guide is moved to its operative position by a remote control device.
In one embodiment of U.S. Pat. No. 3,554,132, the vehicle-engaging members or pushers include tire-engaging rollers or roller dollies secured to a conveyor chain by arms hingedly attached to the conveyor chain. The conveyor chain is located underneath a horizontal track along which a vehicle tire may be located, the track being provided with a longitudinal slot of a size for receiving the arm of the vehicle-engaging member. This slot is enlarged near the forward end of the conveyor course to provide an opening through which a tire-engaging roller may pass to the top surface of the vehicle track. Lifter means are employed for comming the roller from the course of the conveyor, below the vehicle track, upwardly along the track where the roller is then constrained to move. At this time the arm of the tire-engaging member extends through the slot in the track. Toward the end of the conveyor course, the longitudinal slot is enlarged by an opening through which the roller may drop back for return travel below the track.
The vehicle-engaging member or roller dolly of U.S. Pat. No. 3,554,132 is also provided with a second roller located between the tire-engaging roller and the chain along the arm joining the two. This second roller normally aids in carrying a vehicle engaging member along a channel underneath the vehicle track. However, when the tire-engaging roller engages the vehicle tire, this second roller may be urged upwardly to ride along the underside of the vehicle track as shown in FIG. 6 thereof.
Another example of a vehicle conveyor will be described in connection with the prior art device of FIG. 1 and is also disclosed in U.S. Pat. No. 4,374,496 to Hanna which issued Feb. 22, 1983. This prior art device includes a track upon which a roller dolly or pusher is selectively lifted. Three pairs of rollers are provided on the roller dolly. A first pair of rollers are disposed at a predetermined height above the tire track for engaging the tire of the vehicle while being conveyed along the track. The first roller pair pivots about an intermediate roller pair upon contact with a vehicle wheel to a lower position than the position of the initial engagement. The profile of the roller dolly is higher when disengaged from a vehicle tire when riding on the track than when in engagement with the vehicle tire. The roller dolly does not conform to the shape of the sprocket about which the conveyor chain is pulled.
The tire-engaging rollers in U.S. Pat. No. 4,374,496 are coextensive in width with the rollers that ride upon the track and about which the dolly pivots. The high and wide profile of the upper rollers may cause interference with wheel brushes used to clean vehicle wheels that are located close to the track. The wheel brushes are elongate, small-diameter brushes which are brought into engagement with the lower portion of the vehicle wheel as it rolls upon the track. If the dolly used to move the vehicle has a high and wide profile, the brushes may impinge upon the dolly, especially if the dolly disposed on the track but not in engagement with the vehicle wheel. Such contact with the dolly can cause unnecessary wear of the brushes and the dollies.